Biology subjects

Jenni, L.

Publications and source records attributed to Jenni, L..

4 recordsLinked to original sources

bioRxiv2022

How woodcocks produce the most brilliant white plumage patches among the birds

Until recently, and when compared with diurnal birds that use contrasting plumage patches and complex feather structures to convey visual information, communication in nocturnal species was considered to follow acoustic and chemical channels. However, many nocturnal birds have evolved intensely white plumage patches within otherwise inconspicuous plumages. We used spectrophotometry, electron microscopy, and optical modelling to explain the mechanisms producing bright white tail feather tips of the Eurasian woodcock Scolopax rusticola. Their diffuse reflectance was [~]30% higher than any previously measured feather. This intense reflectance is the result of incoherent light scattering from a disordered nanostructure composed of keratin and air within the barb rami. In addition, the flattening, thickening, and arrangement of those barbs creates a Venetian-blind-like macrostructure that enhances the surface area for light reflection. We suggest that the woodcocks have evolved these bright white feather patches for long-range visual communication in dimly lit environments.

ecology↗

bioRxiv2022

Trypanosoma brucei: A novel system for metacyclogenesis and complete cyclical development in vitro

We describe an in vitro system that allows metacyclogenesis of T. brucei ssp. and is not restricted to certain parasite lines. Following the work of Hirumi and co-workers we developed a modified in vitro system which allows metacyclogenesis within 7 to 20 days. The most striking changes were the addition of citrate and cis-aconitate, which triggers transformation from bloodstream to procyclic forms, and the elimination of the remaining bloodstream forms by salicylhydroxamic acid and glycerol. A positive feature of this system is that T. b. gambiense samples isolated from patients, and transformed to procyclic forms for transport, could give rise to infective forms that could be passaged in rodents.

microbiology↗

bioRxiv2019

Survival of adult barn owls is linked to corticosterone levels

Glucocorticoid hormones, such as corticosterone, are fundamental in the translation of external stimuli into physiological adjustments that promote the survival of an organism in face of changes in its environment. At baseline levels, corticosterone is crucial in regulating daily life metabolism and energy expenditure, whereas the acute corticosterone response promotes short-term physiological and behavioral responses to unpredictable environmental challenges. Given their different physiological effects and their role in mediating fitness components, it is still unclear whether and how inter-individual variation in baseline corticosterone levels and acute stress-response levels can affect the survival of organisms. We used 13 years of capture-recapture and dead recovery data combined with 11 years of corticosterone measurements taken on breeding barn owls (Tyto alba) to investigate how survival probability varies in relation to baseline and stress-induced corticosterone levels. Our study shows that males with a higher level of both baseline and stress-induced corticosterone levels have a higher probability of surviving than individuals with lower corticosterone levels. In females, survival probability was higher in individuals presenting elevated stress-induced corticosterone levels but was not significantly associated to baseline corticosterone levels. Our results suggest that in the barn owl the stress-induced corticosterone response is a better proxy of adult survival than baseline corticosterone levels. Further studies investigating the link between corticosterone levels and different fitness components as well as the environmental factors (e.g. weather, development conditions, disease and predation risk) leading to such endocrine phenotypes are needed to identify the costs and benefits of presenting high and low corticosterone profiles.

evolutionary biology↗

bioRxiv2019

Reproductive success in the barn owl is linked to partner compatibility in glucocorticoid levels

In biparental species, reproductive success depends not only on the quality of the parents, the care they each provide and many environmental factors such as territory quality and food availability, but also on the ability of the parents to collaborate and divide reproductive tasks. Because hormones, such as corticosterone (CORT), modulate physiological and behavioural functions that are associated to reproductive success, hormonal compatibility between pair members is likely to have consequences on reproductive success. Here, we investigated in the barn owl (Tyto alba) whether baseline and stress-induced CORT levels are correlated between breeding partners and whether this correlation is associated to fitness parameters (i.e., clutch size, offspring number and body mass). We found that the combination of CORT levels in the two partners predicts reproductive parameters. Pairs with similar baseline CORT levels during incubation produced more fledglings than pairs with dissimilar baseline CORT levels. On the other hand, pairs showing dissimilar stress-induced CORT responses during the period of offspring rearing produced more fledglings than pairs with similar stress-induced responses. Offspring body mass was associated only with maternal (baseline and stress-induced) CORT levels and depended on the context with baseline CORT being potentially adjusted to environmental conditions but also to the energetic demand of reproduction. Hence, to produce large broods good quality mothers might increase their baseline CORT to meet the energetic demand of the brood, while mothers in unfavourable habitats may have smaller broods but still need to increase baseline CORT to cope with the environmental challenges. Taken together, the results show that the association between parental CORT levels and reproductive success are context-dependent and rely on the combination of parental CORT levels. Assuming that CORT levels reflect investment in parental care, our study suggests that parents coordinate their reproductive activities in a complex way to ensure a high reproductive success.

evolutionary biology↗